The rear end gearing will likely play a bigger role in how fast your truck will go than the engine. A 350 should give you all the power you need (perhaps not all you want . . .). It is really remarkable what a good or inventive mechanic can squeeze into an engine bay.

For simplicity and cost effectiveness, a new 350 is a good option. I had one dropped into a 1976 Blazer by a pro and it was a quick swap at under $2000. In response to your question, I would imagine that any 350 will work for you (this is not my area of expertise so listen to Wrenchbender - he's terrific) - what matters is whether it will bolt to your bellhousing on your transmission.

There are lots of discussion threads on increasing horsepower and upgrading brakes and the front end to improve performance, safety, or driving comfort here on the Stovebolt Page. Try using the search tool that is in small print just under the "Post Topic" buttons - you will be amazed at what's available.

Good luck.

~ Kimberly
My '54 ... and my '63 and a '59 F100